Search NASA⌕ Search

SEARCH · Search NASA

Results for “evaluation”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Evaluation of darunavir-derived HIV-1 protease inhibitors incorporating P2' amide-derivatives: Synthesis, biological evaluation and structural studies

Here, we report here the synthesis and biological evaluation of darunavir derived HIV-1 protease inhibitors and their functional effect on enzyme inhibition and antiviral activity in MT-2 cell lines. The P2' 4-amino functionality was modified to make a number of amide derivatives to interact with residues in the S2' subsite of the HIV-1 protease active site. Several compounds exhibited picomolar enzyme inhibitory and low nanomolar antiviral activity. The X-ray crystal structure of the chloroacetate derivative bound to HIV-1 protease was determined. Interestingly, the active chloroacetate group converted to the acetate functionality during X-ray exposure. The structure revealed that the P2' carboxamide functionality makes enhanced hydrogen bonding interactions with the backbone atoms in the S2'-subsite.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Performance evaluation of the three-point angular correlation function

In recent years, we have observed an increase in the diversity of the processors ecosystem. Different designs and architectures are being studied based on their performance and power characteristics. While using benchmarks for this purpose allows for reproducibility and easy understanding of the results, using real scientific applications allows researchers to realize the actual implications of each design on the overall performance of their codes. This paper analyzes the performance of different implementations of a three-point angular correlation function. This function is used in the study of Large-Scale Distribution of galaxies in a variety of computational platforms. The function is based on histogram construction and presents a large computational cost. This cost dramatically increases with the size of the datasets. We have considered two different GPUs, a set of x86 Intel machines (multi- and many-core), ARM chipsets, as well as an FPGA. We first study the best possible implementation for each platform in terms of time to solution. We then compare the power used by those platforms for a predefined number of datasets. Energy is one of the main constraints that computer architects are facing nowadays. The results will be used to evaluate the performance of this function considering those two targets – time and energy – for those platforms and to analyze the suitability of each of those platforms for this specific problem.

Computer Science↗
DOE OSTI2021

Comparative evaluation of deep learning workloads for leadership-class systems

Deep learning (DL) workloads and their performance at scale are becoming important factors to consider as we design, develop and deploy next-generation high-performance computing systems. Since DL applications rely heavily on DL frameworks and underlying compute (CPU/GPU) stacks, it is essential to gain a holistic understanding from compute kernels, models, and frameworks of popular DL stacks, and to assess their impact on science-driven, mission-critical applications. At Oak Ridge Leadership Computing Facility (OLCF), we employ a set of micro and macro DL benchmarks established through the Collaboration of Oak Ridge, Argonne, and Livermore (CORAL) to evaluate the AI readiness of our next-generation supercomputers. In this paper, we present our early observations and performance benchmark comparisons between the Nvidia V100 based Summit system with its CUDA stack and an AMD MI100 based testbed system with its ROCm stack. We take a layered perspective on DL benchmarking and point to opportunities for future optimizations in the technologies that we consider.

Yin, Junqi↗
DOE OSTI2019

Evaluation of the Microstructure and Property of TiNi SMA Prepared using VIM in BaZrO3 Crucible

The contamination from the crucible has been recognized as the main drawback of using vacuum induction melting (VIM) method to prepare TiNi shape memory alloys (SMAs). In the present work, we evaluated the feasibility of utilizing the highly-stable BaZrO3 crucible to prepare TiNi SMAs, whose microstructure and mechanical properties were investigated by High-energy X-ray Diffraction (HE-XRD), analytical Transmission Electron Microscopy (TEM), Differential Scanning Calorimetry (DSC) and tensile test. It was found that there were about 0.035 wt % oxygen and 0.039 wt % zirconium remained in the TiNi alloy after melting in BaZrO3 crucible, which fulfills the ASTM standard on biomedical TiNi alloys. Oxygen from the dissolution of BaZrO3 could form Ti4Ni2Ox phase, and zirconium exists as solute atoms in both of the matrix and second phase. After the thermomechanical processing and vacuum annealing at 850 degrees C, the alloy achieved 37.63% of fracture elongation and 880 MPa of tensile strength. The transformational strain and martensitic yield strain of the alloy reached about 8% and 21% respectively.

Gao, Pengyue↗
DOE OSTI2018

Evaluating Water Reactivity at Silica Surfaces Using Reactive Potentials

Understanding the interactions between amorphous silica surfaces and water provides insight into material degradation of silicate glasses and minerals in aqueous environment. Molecular dynamics (MD) simulations of water and nanometer sized silica structures were used in this work to evaluate the reactivity of flat silica surface and surfaces with curvature. We compared two dissociable water/silica potentials, namely the Reactive Force Field (ReaxFF) and the Mahadevan–Garofalini water/silica force field (MGFF) that have been in development over the past decade, to study their performance in simulating bulk water as well as silica–water interactions. Significant differences in the properties of bulk water as well as surface interactions were observed between the two types of potentials, as well in the same potential type with two parametrizations for ReaxFF, suggesting a need for improvement of the existing water/silica ReaxFF potentials. Our simulation results show that a majority of the silanols were formed by reactions between water and strained siloxane bonds that mainly exist on the surface of amorphous silica, within a few nanoseconds of the simulation time scale, in agreement with previous studies. Effect of surface curvature on the reactivity with water was investigated. Our results indicate that defect concentration at the surface bears a strong correlation to the concentration of silanols (Si–OH) that eventually form. We observe undercoordinated Si’s at the surface that are attacked by water before the hydrolysis reaction of the siloxane bonds and demonstrate possible mechanisms of water reacting with these undercoordinated Si’s. Furthermore, we also find that the method of generating surfaces in simulation determines the defect concentration and hence influences the reactivity of the amorphous silica surface.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Evaluation of E3SM Simulated Aerosols and Aerosol‐Cloud Interactions Across GCM and Convection‐Permitting Scales

This paper introduces an Earth system modeling testbed for predicting aerosols and aerosol‐cloud interactions (ACIs) at convection‐permitting scales. Using the Energy Exascale Earth System Model (E3SM) version 2 with a four‐mode Modal Aerosol Module, we conduct simulations at 3.25 km resolution on a regionally refined mesh (RRM) across four regions with distinct aerosol and cloud regimes. Results are compared with the standard 100 km E3SM configuration and evaluated against satellite, aircraft, and ground‐based observations. We find that increasing model resolution improves heavy precipitation simulation but amplifies positive bias in light drizzle at coarse resolution. These resolution‐induced changes affect cloud and aerosol properties to varying degrees across regions. Generally, cloud cover and liquid water path (LWP) show better agreement with satellite retrievals at 3.25 km, though surface‐based comparisons suggest otherwise. Aerosol composition remains poorly represented at both resolutions. The RRM increases Aitken mode aerosol number concentrations via enhanced new particle formation. However, accumulation mode aerosols are decreased at higher resolution as aerosol removals become more efficient. This partially contributes to fewer cloud condensation nuclei (CCN) and lower cloud droplet number concentrations (N d ), which produces larger model biases in some scenarios. These findings suggest that solely increasing horizontal resolution to kilometer scales is insufficient to broadly improve aerosol and cloud predictions without concurrent advancements in physical and chemical process representations. Nonetheless, the RRM moderately improves key ACI relationships such as CCN‐N d correlation, reflecting enhanced aerosol activation representation. The LWP‐N d relationship is also better captured by RRM, suggesting a better characterization of LWP adjustment.

Huang, Meng [Pacific Northwest National Laboratory↗
DOE OSTI2018

Surface bypass as a means of protecting downstream-migrating fish: lack of standardised evaluation criteria complicates evaluation of efficacy

A surface bypass is a downstream migration structure that can help reduce hydropower-induced damage to migrating fish. We reviewed results of laboratory and field studies conducted in North America, Europe, and Australia between 1982 and 2017 concerning surface bypass efficacy. The main challenges in designing efficient surface bypasses were identified to be the simultaneous consideration of hydraulic and geometrical parameters and biological knowledge of fish behavior. Without the combined efforts of engineers and biologists, an efficient bypass design cannot be achieved. Moreover, the use of different criteria for evaluating bypass performance prevents direct comparison of the results of studies and deduction of design criteria. Bypass efficiency is a term that is widely used, but no standard definition of the term exists. Its definition can thus vary among studies. Two groups of definitions were identified: One group uses only those fish that approach or pass the dam whereas the other group includes all marked or tagged fish that are released upstream of a dam regardless of their fate after release. Within these groups, the definitions of bypass efficiency are comparable. Based on this concept, the efficiencies for different fish species at surface bypasses were identified: eels (11% // 10%), Pacific salmon (46% // 19%), steelhead and brown trout (49% // 41%), and Atlantic salmon (72% // 48%). Currently it is not possible to formulate design criteria for a wide range of species because available data are insufficient data. We recommend that in future bypass studies, more comparable standards and performance criteria should be used and both successes and failures should be reported.

Klopries, Elena-Maria↗